This invention relates generally as indicated to a system for determining the dynamic orientation of a vehicle wheel plane and more particularly to a system wherein off-vehicle measurement equipment is used to determine the orientation of the wheel plane while the vehicle is being driven.
The trend in the tire and automobile industry is to closely match and design a particular tire as original equipment for a particular vehicle. Specifically, automobile manufacturers commonly equip a vehicle with a set of tires which have been found to provide the most desirable wear and ride characteristics for that particular vehicle. To this end, a number of tests are performed on tires to determine their suitability for a specific vehicle. Of particular relevance to the present invention are the tests that are performed to obtain dynamic orientation characteristics of a wheel on which the tire is mounted.
The dynamic orientation of a wheel plane is defined by two angles, namely the inclination angle and the heading angle. The inclination angle relates to the xe2x80x9ctiltxe2x80x9d of the wheel with respect to the ground and can be defined as the angle between the plane of the wheel and a plane perpendicular to the ground. The heading angle is the angle between a reference direction on the ground and the travel direction of the wheel.
An apparatus for measuring the dynamic inclination angle of a vehicle wheel is disclosed in U.S. Pat. No. 5,561,244. (This patent is assigned to the assignee of the present invention.) The disclosed apparatus includes a bracket non-rotatably mounted to the wheel and extending in horizontal cantilever fashion therefrom. Laser transducers are appropriately mounted on the bracket to emit beams against the road surface and to detect the beams reflecting back from the road surface. Sensors measure the distance from the ground and these measurements are fed through control cables to a computer located within the vehicle. The angular change of the bracket is representative of the change of the inclination angle of the wheel. In this manner, the apparatus obtains the dynamic inclination angles which the wheel experiences as it is driven along an actual road surface on a particular vehicle.
In the apparatus disclosed in U.S. Pat. No. 5,561,244, the measuring equipment (i.e., laser transducers, sensors, etc.) must be mounted to the vehicle, this sometimes sensitive equipment is exposed to the risks of damage due to moving contact and/or reduced accuracy issues. Moreover, the apparatus disclosed in U.S. Pat. No. 5,561,244 cannot measure and/or take into account the heading angle of the wheel since the sensors are moving with the vehicle whereby it cannot determine the dynamic orientation of the wheel plane.
The present invention provides a system for measuring the dynamic orientation of a wheel plane while the vehicle is being driven but without the need to mount orientation-determining equipment to or on the vehicle. In this manner, orientation measurements can be obtained which correspond to the real-world environment (such as vehicle compliances and driving conditions) while at the same time the measuring equipment is not exposed to the risks or problems associated with on-vehicle mounting. Moreover, the system of the present invention can measure not only the inclination angle but also the heading angle of the wheel whereby the dynamic orientation of the wheel plane can be determined.
More particularly, the system of the present invention comprises a test surface on the vehicle (such as disk secured to the hub of the wheel) and an orientation-determining device unattached to the vehicle. The test surface rotates with the wheel when the vehicle is being driven and is positioned in a plane corresponding to the orientation of the wheel plane. The orientation-determining device, which can be stationary, determines the orientation of the plane of the test surface at a specific point of time while the vehicle is being driven. In this manner, both the inclination angle and the heading angle are taken into account during the measurements and can be used when evaluating the dynamic orientation characteristics of the wheel.
A processor can be provided to receive signals from the orientation-determining device and convert the signals into output data corresponding to the orientation of the wheel plane for the specific point in time. The orientation-determining device can be a device which em its non-collinear beams of energy onto the test surface. For example, the orientation device can comprise at least three transducers which emit respective beams of electromagnetic energy (e.g., laser beams) to three non-collinear points on the test surface and which detect respective beams reflected off of the test surface and thereby determine the distance of each of the three non-collinear points from the device.
To use the system of the present invention, the vehicle is driven (e.g., accelerated, braking, cornering and combinations thereof) past the orientation-determining device and the orientation-determining device is activated to obtain data indicative of the orientation of the plane of the test surface.